At the present time the theft of automobiles (cars) is an important problem. Despite the best efforts of auto manufacturers, car theft device manufacturers, and the police, car theft remains as one of the most prevalent crimes, resulting in the loss of billions of dollars and high car theft insurance in many areas.
Car manufacturers now produce cars with various anti-theft devices, such as locked steering wheels, keys with microprocessor chips, and remote control locks. In addition, various steering wheel locks and bars are widely used. Another anti-theft system uses a radio transmitter hidden on the car which is activated when the car is reported as being stolen. Despite these devices car theft is still a problem. Many of these devices are useless in a "car jacking" situation in which the car owner is accosted, his keys taken and his car stolen.
When a car is stolen it may be reported to the police almost immediately, for example, if a car is stolen from a mall parking area. The police would be notified of the car's description, ie., "a white 1995 Acura Legend four-door" and its license number, i.e., New York "JWB 123". However, the thief, to prevent being caught, may switch the original license plates with license plates he has brought with him. Consequently the police would not be able to detect and stop the stolen car.
Another problem in traffic law enforcement is to prevent the use of false or switched license plates. For example, someone who does not have a legal license plate, for example, because of his non-payment of insurance, may steal or otherwise obtain license plates from another car, place them on his car and drive with the switched plates.
The issued U.S. patents mentioned below are incorporated by reference. U.S. Pat. No. 4,947,353 uses a scanning laser, which scans at 160 times per second, on one side of a roadway, and a vertical elongated photoelectric detector on the other side, to measure the heights of vehicles. U.S. Pat. No. 5,088,827 discloses a system for measuring the width of a traveling object, such as a wire, being manufactured. U.S. Pat. No. 5,083,200 relates to using a linear camera for obtaining the silhouette of a traveling vehicle to determine if it is a truck etc., using its length and height. U.S. Pat. No. 5,381,155 uses a license plate reader, a speed measuring device, a data base of registered vehicles and a variable message sign to display the names of speeding drivers on the sign. In U.S. Pat. No. 5,066,950 two spaced-part infra-red beams are used to indicate the speed, length and separation of traveling vehicles for photographing speeding vehicles.
The following U.S. patents relate to reading license plates and generating digital signals representing the plate numbers: U.S. Pat. Nos. 4,567,609; 4,817,166; 5,081,685; 5,136,658; 5,175,617; 5,204,573; 5,204,675; 4,731,854; 4,878,248; 5,315,664; 5,425,108